1. Field of the Invention
The present invention relates to a ball grid array integrated circuit package.
2. Description of Related Art
Integrated circuits (ICs) are typically located within a package that is mounted to an external printed circuit board. There has been developed a low profile IC package commonly referred to as a ball grid array (BGA). BGA packages typically contain a substrate that has a plurality of external bond pads located on a bottom surface. Individual solder balls are attached to the external pads of the substrate. The BGA package can be subsequently assembled to a printed circuit board by soldering the solder balls onto corresponding pads of the board. The BGA substrate typically contains internal vias and routing that couple the bond pads to an integrated circuit mounted to the top surface of the substrate.
FIG. 1 shows routing for the top surface of a prior art BGA substrate. The substrate has an inner die paddle 1 which is typically dedicated to electrical ground. Concentric with the die paddle 1 is a voltage bar 2 that is typically dedicated to the voltage source of the integrated circuit. Located around the die paddle and voltage bar are a plurality of bonding fingers 3. The bonding fingers 3 are typically dedicated to the input/output (I/O) signals of the integrated circuit. The bonding fingers 3 are routed to vias 4 that are connected to external bond pads (not shown) located on opposite side of the substrate. An integrated circuit is mounted to the center of the substrate and connected to the voltage bar 2 and bonding fingers 3 by a number of wire bonds (not shown).
The bonding fingers are arranged into four different segments which each have a slight radial pattern. Newly developed integrated circuits continually require additional I/O pins. Increasing the I/O of the package typically requires a larger radius for the radial pattern of bonding fingers. To maintain a minimum wire length of the wire bonds, the outer dimensions of the integrated circuit die must be increased to match the larger radius of the bonding finger pattern. The increase in die dimensions increase the overall size of the package. It would be desirable to increase the I/O of a BGA package while maintaining or even decreasing the size of the integrated circuit die.